No, this is the proper way to handle accusations from someone who may not be credible. You investigate privately, and only report after, if the accusations seem credible. You don't blast across the media that so-and-so is accused of sexual assault, because then the damage is done, regardless of the truth. Signal boost it enough, and every lay-person's main association with the person will become, "oh, that guy accused of sexually assaulting his sister".
The accusations are about events 25 years ago, when they were children. No one will ever be able to disprove this, so there's no way to undo the reputational damage.